Linux / Unix: time Command Examples

I am new Linux and Unix systems user. How do I display the time of the execution of a command/script on Linux or Unix-like operating systems using shell prompt? You need to use the time command to display the elapsed time during the execution of a command or script.

A note about GNU/Linux time command

GNU/Linux user can use the following syntax to write the resource use statistics to file instead of to the standard error stream:$ /usr/bin/time -o output.time.txt -p date $ cat output.time.txt Pass the -a option to append the resource use information to the output file instead of overwriting it. This option is only useful with the -o option:$ /usr/bin/time -a -o output.time.txt -p sleep 2 $ cat output.time.txt You can control time command output format using -f FORMAT as follows:$ /usr/bin/time -f 'FORMAT' -p command Use FORMAT as the format string that controls the output of time as follows:

Fomat

Meaning

%

A literal `%'.

C

Name and command line arguments of the command being timed.

D

Average size of the process's unshared data area, in Kilobytes.

E

Elapsed real (wall clock) time used by the process, in [hours:]minutes:seconds.

F

Number of major, or I/O-requiring, page faults that occurred while the process was running. These are faults where the page has actually migrated out of primary memory.

I

Number of file system inputs by the process.

K

Average total (data+stack+text) memory use of the process, in Kilobytes.

M

Maximum resident set size of the process during its lifetime, in Kilobytes.

O

Number of file system outputs by the process.

P

Percentage of the CPU that this job got. This is just user + system times divided by the total running time. It also prints a percentage sign.

R

Number of minor, or recoverable, page faults. These are pages that are not valid (so they fault) but which have not yet been claimed by other virtual pages. Thus the data in the page is still valid but the system tables must be updated.

S

Total number of CPU-seconds used by the system on behalf of the process (in kernel mode), in seconds.

U

Total number of CPU-seconds that the process used directly (in user mode), in seconds.

W

Number of times the process was swapped out of main memory.

X

Average amount of shared text in the process, in Kilobytes.

Z

System's page size, in bytes. This is a per-system constant, but varies between systems.

c

Number of times the process was context-switched involuntarily (because the time slice expired).

e

Elapsed real (wall clock) time used by the process, in seconds.

k

Number of signals delivered to the process.

p

Average unshared stack size of the process, in Kilobytes.

r

Number of socket messages received by the process.

s

Number of socket messages sent by the process.

t

Average resident set size of the process, in Kilobytes.

w

Number of times that the program was context-switched voluntarily, for instance while waiting for an I/O operation to complete.

Why are we using /usr/bin/time? when not using any options simply writing time is working but when should we go for /usr/bin/time when using options? This is working but i dont understand the logic. when : time -o output.txt ls //is used i am getting error as no bash command -o /usr/bin/time -o output.txt ls //is working fine

Got the answer. time simply referes to time command of bash which has no options. /usr/bin/time referes to the time command which this tutorial is speaking about. bash time command help: help time, normal time command help: man time